Population by age and sex, England and Wales, 2011

BBC home editor Mark Easton says the most likely reason for the discrepancy between the official estimate and the actual population is inaccurate migration data.

It is notable that the number of people in their 20s has risen from 6.6m to 7.6m - that additional one million people are most likely to be migrant workers, he adds.

The latest rise compares with a rise in population of 1.6 million between 1991 and 2001.

The population projections published by the ONS will be revised upwards in the autumn.

On the night of the census there were 23.4 million households in England and Wales, with the average household size being 2.4 people per household in 2011, just over half of the 4.3 residents per household 100 years earlier.

The 2011 Census also showed the average population density was 371 people per square kilometre; however, in London this figure was 5,200.

If the London figures were excluded, the average population density for the rest of England and Wales was 321 people per square kilometre, the ONS said.

All regions saw population growth between 2001 and 2011, with the highest growth in London, the East of England and the East Midlands.

Other population data showed:

Analysis

By Mark EastonHome editor

There are almost half a million more people living in England and Wales than official estimates suggested. The most likely reason for that under-counting is inaccurate migration data.

It is notable that the number of people in their 20s has risen from 6.6m to 7.6m - the additional one million people are most likely to be migrant workers.

The increase in the number of under-fives by 400,000 is also a consequence of immigration, but increasing fertility among British-born women is the key driver in pushing up the fertility rate.

Half of the total increase in population was in London, the South-East and East regions of England.

The Office for National Statistics says that about 55% of the population increase was the result of net migration.

The population projections published by the ONS will be revised upwards in the autumn.

The public were asked questions about their jobs, health, education and ethnic background. It was the first time people could fill in the form online.

The form was compulsory, but a question about religion was optional. The answers are used to plan public services.

Three different censuses happened on the one day. Northern Ireland and Scotland each managed their own, and these were run separately from the one which was sent to 25.4 million households in England and Wales.

Northern Ireland's population rose to 1.81 million - the highest figure ever - according to its census.

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The number of people increased by 7% over the last decade, broadly in line with the figure for England and Wales.

The just-published figures showed an increase in the proportion of elderly people and a decrease in the percentage of children under 16.